1. Field of the Invention
The present invention relates to a sheet processing apparatus which can selectively process a sheet received from a main body of an image forming apparatus and, more particularly, to a sheet processing apparatus having a plurality of stacks which stack sheets thereon.
2. Description of the Related Art
Some of conventional image forming apparatuses such as copying machines or printers are provided with a sheet processing apparatus which can sequentially receives sheets, each having an image formed thereon, and then, selectively subjects the sheets to a binding process. A sheet processing apparatus disclosed in, for example, Japanese Patent Application Laid-open No. 4-128096 is of a console type installed directly on a floor. At an upper portion of such a sheet processing apparatus are arranged a plurality of elevatable stack trays for assorting sheets. Inside of a body at a lower portion of the apparatus is housed a sheet processing portion having a stapling function in a vertical direction. A sheet received from a main body of the image forming apparatus is separately conveyed onto either one of upper and lower conveying paths by a switching member. The sheet conveyed above is separately stacked on the elevatable stack tray. In contrast, the sheet conveyed downward passes through a lower U-shaped path, on which the sheet is oriented upward at the tip thereof, and then, is conveyed onto an intermediate stack portion vertically housed inside the body of the apparatus. The sheets conveyed onto the intermediate stack portion are bound together after alignment. Thereafter, the bundle of sheets is pushed up at the rear end thereof by a belt member, to be then discharged to a discharge tray.
However, since the sheet processing portion including the intermediate stack portion in the conventional sheet processing apparatus disclosed in Japanese Patent Application Laid-open No. 4-128096 is configured in the vertical direction on an apparatus installation plane, the apparatus is increased in vertical size.
In order to miniaturize the vertical size of the sheet processing apparatus, it is construed that a distance between the intermediate stack portion and the stack tray disposed above the intermediate stack portion is reduced as possible. However, since the intermediate stack portion is configured in the vertical direction, as described above, the mere reduction of the distance causes the tip of the sheet to enter under the upper stack tray when the sheet is discharged from the intermediate stack portion, thereby raising an accident of jamming. In view of this, it is necessary to form a clearance between the intermediate stack portion and the upper stack tray enough to prevent the sheet from being jammed, thereby making it difficult to miniaturize the apparatus.
Furthermore, in order to miniaturize the vertical size of the sheet processing apparatus, it is construed that the intermediate stack portion is disposed in a lateral direction along the upper stack tray. However, a mere proximity between the intermediate stack portion and the upper stack tray possibly causes an accidental touch to the sheet being aligning on the intermediate stack portion or erroneous withdrawal of the sheet when a user accesses the sheet on the stack tray.